Hitherto, for an electrophotographic light-sensitive material, an inorganic photoconductive material such as selenium, selenium alloy, zinc oxide, cadmium sulfide etc., has been mainly used. However, in the electrophotographic light-sensitive materials using the inorganic photoconductive materials, there are problems in the points of producibility, production cost, flexibility of the light-sensitive material, etc.
Recently, for solving the problems accompanying the inorganic photoconductive materials, there are known electrophotographic light-sensitive materials using organic photoconductive materials such as polyvinylcarbazole-2,4,7-trinitrofluorenone (TNF). Furthermore, recently, laminated layer-type electrophotographic light-sensitive materials formed by the combination of one or more kinds of pigments such as perylene series pigments, perinone series pigments, phthalocyanine series pigments, azoic pigments, etc., or dyes such as cyanine dyes, pyrylium salt dyes, thiapyrylium salt dyes, squarylium salt dyes, etc., as charge generating materials and one or more kinds of charge transfer materials such as pyrazoline, hydrazone, triallylamine, stilbene, etc., are proposed as disclosed in JP-A-58-16247 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
However, the electrophotographic light-sensitive materials using these organic photoconductive materials have a low light-sensitivity and hence are yet insufficient as light-sensitive materials.
Also, a laminated layer type electrophotographic light-sensitive material separating the function into a charge generating layer and a charge transfer layer has been proposed but satisfactory light-sensitive materials of this type have not yet obtained.
That is, in a conventionally proposed laminated layer-type electrophotographic light-sensitive material having a charge generating layer and a charge transfer layer laminated, in succession, on a conductive support, the light-sensitivity is yet insufficient and there are problems that the light-sensitivity and the charged potential largely change with the change of environmental circumstances and the potential cycle deviation between an exposed portion and an unexposed portion is large.
Such a problem is also seen in an ordinary process of developing non-image portions on a photosensitive material with toner and transferring the toner images onto a transfer material such as paper, but the problem becomes remarkable in an image forming process including the steps of forming electrostatic latent images by uniformly negatively charging an electrophotographic light-sensitive material and imagewise exposing the light-sensitive material, forming toner images by toner development, and applying positive charges onto the light-sensitive material at the transfer of the toner images onto a transfer material such as paper. That is, since the potentials at the exposed portions and the non-exposed portions of the aforesaid light-sensitive material cause great cycle deviations, the density of the transferred images differs greatly between the initial image and images after copying many copies and fog is formed on the transferred images, as well as when after copying a large amount of copies, the size of transfer papers is changed to a larger size, there are problems that the transferred density at the widened portions of the large-sized transfer papers becomes high and fog is formed in these portions.